Man Retrofits Freezer to Make an Ultra-Efficient Fridge (0.1 kWh) per day
 

http://i.treehugger.com/files/images/freezer.jpg

An off-grid experimenter in Australia, Tom Chalko, has retrofitted a chest freezer to create a fridge that uses only 100 watt-hours (0.1 kWh) per day! Why a chest freezer? Tom points out that vertical door refrigerators are inherently inefficient. As soon as you open a vertical fridge door the cold air escapes, simply because it is heavier than the warmer air in the room. When you open a chest freezer, the cool air stays inside, just because it�s heavy. Any leak or wear in a vertical door seal causes significant loss of efficiency.

Tom took a standard chest freezer (a Vestfrost SE255), added a $40 external thermostat, then wired the freezer to turn off when the desired temperature was reached. The thermostat runs on 2 AAA batteries which last for months. The freezer runs for about 90 seconds per hour and then shuts down completely, making it not only very efficient but very quiet.

Re: Man Retrofits Freezer to Make an Ultra-Efficient Fridge (0.1 kWh) per day
 

Ingenious!

Re: Man Retrofits Freezer to Make an Ultra-Efficient Fridge (0.1 kWh) per day
 

:cool2: Nice idea...even off the grid that thing is efficient.

Back in the old days the people in the mountain regions used to divert cold mountain springs and small creeks close to their house for use as a home built refrigerator...without the refrigerator.

No reason it won't still work today.

:cool2: :cool2: :cool2:

Re: Man Retrofits Freezer to Make an Ultra-Efficient Fridge (0.1 kWh) per day
 

I'm not making any sense of this. Either the compressor is running or it isn't. The article makes it sound like the savings come in when the unit is not running.

Re: Man Retrofits Freezer to Make an Ultra-Efficient Fridge (0.1 kWh) per day
 

I thought that part was about the thermostat. Where it only really consumes large (relative to a AAA battery lasting months) amounts of power when it switches.

Seems like a good idea to me. Some things would be harder to get at from above, but I think it would work great at doing what it is supposed to do.

Re: Man Retrofits Freezer to Make an Ultra-Efficient Fridge (0.1 kWh) per day
 

QWAK,hoarder is right! An external thermostat would make no difference!

I took a 1902 Ice box and turned it in to a modern refrig/freezer but the air leaks on door gaskets was a problem I could never solve so it was never FROST FREE and had to be defrosted evey mo. or two.

I expected to read that he added 4" of high dencity foam to out side which would be r 48 over what freezer came with which today is about r 48,
that may have improved efficiency but just adding a thermostat would NOT improve efficiency.

the DUCK

Re: Man Retrofits Freezer to Make an Ultra-Efficient Fridge (0.1 kWh) per day
 

Freezers don't draw much amperage when the compressor is not running. When the compressor is off, the only thing using electricity is the AC thermostat which would be milliamps. The article is puzzling.

Re: Man Retrofits Freezer to Make an Ultra-Efficient Fridge (0.1 kWh) per day
 

What refrigerators need are a bunch
of small see-thru doors inside the
big opaque door. Or perhaps narrow
pullout drawers like I see in movies
at a morgue, only smaller. Some day,
..... you'll see 'em.

dtnwn

Re: Man Retrofits Freezer to Make an Ultra-Efficient Fridge (0.1 kWh) per day
 

Don't all freezers have built in thermostats? My refrigerator does.
If it's just an ordinary compressor motor, most of the energy requirement
is at start up, isn't it? I think Duck and Hoarder are right.
Insulation, seals and door on top all make sense.
Maybe this guy keeps his freezer inside a big freezer.
Unless I'm missing something.

Re: Man Retrofits Freezer to Make an Ultra-Efficient Fridge (0.1 kWh) per day
 

It would make sense off grid if the DC thermostat/relay operated a remote generator start/stop to kill the generator whenever the compressor didn't need to run. In such a case a DC thermostat/relay would be needed since the AC thermostat would be inoperative with the generator off.

Re: Man Retrofits Freezer to Make an Ultra-Efficient Fridge (0.1 kWh) per day
 

QWAK,I still have an ANTIQUE gas refrigerator that was made in the 30s:hahaha: (a guess) heavy steel with heavy baked enamal inside and out ,STILL WORKS even makes ICE! :) works by HEATING amonia and allowing the high pressure gas to escape in to an expancion coil threw a small oraface. Seemed kool to me that you could make things COLD by burning GAS! :albertein

I ran it for several years on propain now I just store my welding rods in it. Thing weighs a TON --- they don't build them like that no more! :getdown: The new ones are way more efficient but all plastic and foam with a very thin metal shell. Not many will be around to see 20 years let alone 70+ and still be working! :wavey:

I like old stuff it was made to be fixed not thrown away! :beer:

the DUCK

Re: Man Retrofits Freezer to Make an Ultra-Efficient Fridge (0.1 kWh) per day
 

QWAK,horder,I highly dbout that if he was runing a generator to power the freezer that it would be ENERGY EFFICIENT, the power loss would be enormous plus the generator would have to be only prpducing JUST what the freezer needed and not have power waisted which is just not realistic.

It was a FREEZER so the factory instaled thermostat would be the most efficient at monitering the inside temp. A second thermostat would be redundent and less eficient becaise it is located OUT SIDE the box so sencor lines would have to pass threw box to indide to moniter temp.

Whole thing sounds BOGUS to me! If adding an externan thermostat made it more efficient THAT is ware they would put them in the first place! DAUH!!!!:albertein :hahaha:

the DUCK

Re: Man Retrofits Freezer to Make an Ultra-Efficient Fridge (0.1 kWh) per day
 

Bingo. Maybe they're trying to promote this bozo to public office or something.

I detect a new conspiracy.....
 

Now I know nothing about electricity or electronics or appliances but let me tell you this. You electrician guys dont want to tell "THE TRUTH" about this. It's really just a CONSPIRACY. If you let told people "THE TRUTH" then you would all be out of a job!!!!

What I do, see, is I ignore what the electricians and engineers say, they just have a piece of paper that they say makes them an expert, and I go off and try and reinvent the wheel myself. I'm sure I can do this too, and I would bet my freedom and my savings upon it.

While I'm at it, I feel I should stop going to the dentist and start drilling my own teeth. I have a blackanddecker that will do just fine and I will melt a round next time I get a cavity and like, just pour the molten stuff into the hole I bore in my rotten tooth. I will take some willow bark or something to kill the pain, sterilize it with a shot of whiskey, and bingo! One or two teaspoonfuls of collodiale silver to ward off infection and Ill be OK. :D You know dentists are just in it for the money, if people knew how easy it was to fix your own cavities then they would lose their racket right..... I mean whats the worst, thing, you just get some pliers and out it comes if you screw up... barbers used to do this before "dentists" right...


Ahh... just kidding... nobody here would be so idiotic.... would they????

Re: I detect a new conspiracy.....
 

Grandma used to make us swish a shot of whiskey around when we had a toothache til we'd get to the dentist. Irish remedy. Worked well, but hated it like you wouldn't believe. Probably she knew we just wouldn't complain about it too much cause we knew the remedy:wink: . Anyway ,now they'd probably jail her for child abuse or something I guess.

Re: Man Retrofits Freezer to Make an Ultra-Efficient Fridge (0.1 kWh) per day
 

:cool2: OK...here's the technical reality.

Just thinking out loud here...I'm used to dealing with 500-1200 ton industrial chiller units and commercial HVAC refrigeration equipment.

Chest type freezers are a better choice for less power consumption than any upright. His choice of design is valid.

Freezers by design are constructed with better grade insulation and an ultra low range thermostat control....usually a mercury bulb type.

I get the distinct idea he only replaced/disconnected the internal thermostat from the inline compressor start/stop circuit and replaced it with a higher temperature range type.

There are dozens of ways to accomplish the same result...even a mechanical bimetal type is feasible for direct starting of the compressor.No voltage required.
Find the right temperature range and mount the sucker so it can sense wall temperature.Cut a hole in the freezer sidewall and insulate it from violent ambient swings of surrounding temperature and it should work quite well.
The fact that he used a low voltage DC type with a sensing bulb in the freezer compartment could have been the only method he thought of to circumvent continuous amp draw of the original low range factory thermostat.

Any low voltage AC thermostat would have accomplished the same effect,but would require a step down transformer in the circuit to reduce the operating voltage. That's not real bright because the energy loss of the transformer itself would be horrendous.

So the external self powered DC type thermostat would begin to make better sense from an energy conservation standpoint.

I am just guessing here, but in essence he probably discovered a freezer makes a better,more efficient refrigerator than an off the shelf generic refrigerator.

Just raise the desired inside compartment operating range from zero degrees to 40 degrees and the compressor runs at idle only occasionally.

Figure about 15 amps max on the compressor for a starting load on a low voltage DC thermostat and you're good to go.

BTW: HVAC thermostats with battery power are as common as dirt.

The newer digital models don't use line voltage for power,reference or control switching.

Overall...not a bad idea...at least he's thinking.

Re: I detect a new conspiracy.....
 

Why doesn’t a truly efficient refrigerator or freezer incorporate a vacuum, much like a thermos? After a certain temperature is achieved and the cooling process stops, a vacuum pump would create a barrier whereby the cold molecules would have an extremely small area of contact with the ambient outside temperature.

It works for the old beverage thermos.

The only drawback that I could see, would be waiting five or ten seconds for the frig to depressurize, before opening the door.

Re: Man Retrofits Freezer to Make an Ultra-Efficient Fridge (0.1 kWh) per day
 

I think his calculations on energy consumption are too optimistic.

100 watt/hr per day ... ? Surge current (starting currenct) for a 1/5 hp compressor is higher than that.

But it is a good idea. Another idea was to take an old chest freezer and install a copper coil in it and have the well pump its water thru it before the expansion tank.

Re: Man Retrofits Freezer to Make an Ultra-Efficient Fridge (0.1 kWh) per day
 

:cool2: Let's see....

90 seconds X 24hrs = 2160 seconds / 60 = 36 minutes X 187 watts(1/4 hp) /60 minutes =3.11 watt minutes X 36 = 112 watts

Hmmm...I see how he arrived at the 1/10 KW estimate.

But....ballparking the figures.Conservative surge multiplier...

Surge start watts 1.5 X 187 = 280 X 24 cycles = 6720 watts

I agree with Halo...watts is watts...the time spread is cumlative.

He forgot to add the start load to the total efficiency
Looks more like 6832 watts per 24 hrs..

6832 /3600 = 1.90 watt hrs.

Grand total approx .3 KWH instead of the .1 he is claiming.

Still not half bad....check my math Halo...I'm getting sleepy...

:cool1: :cool1: :cool1: :cool1:

Re: I detect a new conspiracy.....
 

QWAK,A vacuum chamber big enough to hold the contents of a chest freezer would have to be built out of 1/2" steel or thicker to avoid the out side air pressure crushing it flat!:albertein :hahaha:

the DUCK

Re: Man Retrofits Freezer to Make an Ultra-Efficient Fridge (0.1 kWh) per day
 

His duty cycle calculations are stretched. 90 sec for 24hrs ?????

Maybe if its loaded with hot ice ... or sitting on the back porch in 20 degrees ...

Re: Man Retrofits Freezer to Make an Ultra-Efficient Fridge (0.1 kWh) per day
 

That's 90 seconds times 24 hours, not 90 seconds every 24 hours.